This invention relates to current interrupters of the type used in controlling fault currents associated with transmission lines in power distribution systems. More particularly, the invention relates to such interrupters employing a housing filled with a dielectric fluid.
Fast-acting current interrupters are used on power distribution lines for current limiting purposes. Fault currents on high voltage lines, due to ground shorts, for example, can rapidly become enormous and cause serious equipment damage. As transmission voltages rise, there is a continuing need in the electric power industry for improved current interrupting devices and methods for use in rapidly controlling fault currents.
Current limiting circuits employ interrupter switches which open to divert a fault current through an associated current-suppressive impedance which limits the current to a safe level. A common feature of most types of interrupters is that arcing occurs between the electrodes when the contacts are opened. Since the arc will carry substantially the full fault current, the voltage drop between the arcing electrodes must be large to successfully divert the fault current into a parallel impedance. It is known that submerging the arcing electrodes in a dielectric medium can increase the voltage drop. However, the large amounts of energy released by arcing electrodes can vaporize or otherwise reduce the effectiveness of dielectric fluids.
Rapid separation of the contact electrodes is desirable to prevent damaging current increases. Mechanical or magnetic actuating means for separating electrodes generally take on the order of two milliseconds to effect separation. Mechanical-type actuators also have the associated problems of contact bounce and generally high cost. Chemical explosives have been used to break contacts to effect rapid breaking of a circuit. A problem which arises when explosive charges are employed to fracture or break current-carrying material is that the resultant arcing gap is non-uniform and fragmented. This leads to numerous sharp edges and other surface features which can result in an efficient arcing environment, producing a low voltage drop between the electrodes. Furthermore, such destructive use of explosives generally renders the device non-reusable.